A differential housing supports a differential mechanism having gears that transmit torque from a transmission of a vehicle to axle shafts of the vehicle. Generally, bevels gears of the differential mechanism are housed in the differential housing. Alternatively, planetary gears can also be housed in the differential housing. The typical differential mechanism of the vehicle transmission is designed to transmit torque from a transmission output to opposing axle shafts of the differential mechanism allowing right and left wheels to rotate at different speeds, particularly important when negotiating a turn. While performing generally the same function, the differential mechanism has different dimensional requirements for rear wheel and front wheel drive vehicles. Specifically, differentials intended for use on the front wheel drive vehicles require a beveled, and even annular shape in order to compensate for both the smaller packaging area available and to account for the steering characteristics of the front wheels of the vehicle.
The art is replete with various methods of forming the aforementioned differential housings. The differential housings can be formed from a single casting that is machined subsequent to casting. The casting process enhances the control of wall thickness but produces a relatively heavy finished part. An continuing goal of vehicle manufacturers is to reduce the weight of each component of the vehicle. Flow forming is a process that can produce relatively lighter finished parts, but is limited with respect to the control of wall thickness. U.S. Pat. No. 6,061,907 to Victoria et al. discloses a method for forming a two-piece differential housing using a cold flow-forming process. In particular, a housing portion is formed in a series of steps starting with a cup-shaped workpiece. The cup-shaped workpiece is fitted over a mandrel and flow-formed into a housing preform. Surface finishing is performed during the flow-forming process. Flow-formed differential housings can sometimes be compromised by sections of thin walls. These thin wall sections diminish the durability of the differential housing.
There is a constant need in the area of differential housings for an improved design of the differential housing formed by the cold flow-forming process that improves durability characteristics of the differential housing.